This invention relates to the making of sections or sleeves of sheaths of heat-skrinkable plastic, intended to be placed then heat-shrunk around containers. More particularly, the invention relates to a novel apparatus making possible the continuous, high rate production of such sleeves from a continuous flat sheath strip, the shaping of these sleeves to conform to the containers to be covered and then their automatic placement around these containers.
It is well known to provide containers, such as bottles, aerosol bombs, flasks, food cans and similar objects, of various materials, with a sleeve or protective covering of shrinkable plastic. This sleeve is placed in a relatively loose condition around the container and, after heating to cause shrinking of the plastic, it should perfectly fit the contour of the container. Thus, there are made containers, generally printed, provided with sleeves of transparent thermoplastic or a porous or cellular plastic.
Numerous operating steps are necessary to obtain from the thin plastic sheet, for example of polyvinyl chloride, made heat-shrinkable, a sleeve and fit it to a container provided with its decorated covering. These steps should be automated to achieve a suitable industrial profitability. According to the technique thus far currently used, a plastic film is made into a continuous sheath or covering, then sheath sections are cut in appropriate dimensions and the resulting sleeves, stacked horizontally or vertically in a magazine, are used to feed a machine making it possible to extract the sleeves individually then open them to the desired conformation and place them around the containers to be covered which travel on a conveyor. The sleeves then are subjected to heat-shrinking. This technique is known from French Pat. No. 76.05033 of Feb. 24, 1976 and French Patents of Addition Nos. 76.33691, 77.00209 and 77.19565. The technique is also disclosed in U.S. Pat. No. 769,748.
This known technique is certainly satisfactory but the apparatus for using the sleeves is difficult to regulate, which detracts from its reliability. Furthermore, production rates are relatively limited because of the complexity of the step and stages for opening the sleeves. Finally, the presence of two fold lines on the sleeves placed on the containers creates difficulties during the final heat shrinking operation.